German brewers have warned Chancellor Angela Merkel that any law allowing the
controversial drilling technique known as fracking could damage the
country's cherished beer industry.

The Brauer-Bund beer association is worried that fracking for shale gas, which involves pumping water and chemicals at high pressure into the ground, could pollute water used for brewing and break a 500-year-old industry rule on water purity.

Germany, home to Munich's annual Oktoberfest - the world's biggest folk festival which attracts around 7m visitors - has a proud tradition of brewing and beer drinking.

Under the "Reinheitsgebot", or German purity law, brewers have to produce beer using only malt, hops, yeast and water.

"The water has to be pure and more than half Germany's brewers have their own wells which are situated outside areas that could be protected under the government's current planned legislation on fracking," said a Brauer-Bund spokesman.

"You cannot be sure that the water won't be polluted by chemicals so we have urged the government to carry out more research before it goes ahead with a fracking law," he added.

Germany is Europe's biggest producer of beer and has the third-largest per-capita consumption after the Czech Republic and Austria.

It is home to more than 1,300 breweries, which produce about 5,000 different beers, according to the Brauer-Bund.

With pressure mounting from German industry to at least look into the option of tapping its shale gas reserves, Merkel's centre-right coalition is working on a law setting out the conditions for exploration that would protect certain areas.

Given resistance from opposition parties which could block the law in the upper house of parliament, it is unlikely that a law on fracking will be passed before an election in September.